The next major Western nation?
The way things fell out just lately, probably Denmark
I dunno if they'll hit Britain twice..
Besides, it's not as if it's some big master plan being orchestrated by Bin in a mountain bunker, like Blofeld in his extinct volcano lair. It's thought up by a gang of youths in their local mosque. The only thing to come out of main central command is ideology, the rest is up to the followers.